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Torsion pendulum

  1. Dec 2, 2011 #1
    1. The problem statement, all variables and given/known data

    i did my experiment on torsion pendulum and there is a graph that i am supposed to draw ( C as a function of 1/L) where C is the tosion constant and L the length of the wire after that they give me a formula C=1/32L *∏*G*a^4 where G is called the modulus of rigidity and a is the diameter of the wire my purpose is to find G

    2. Relevant equations
    1) i just want to know the expected result of G because i got 300 Pa??
    2) how to find the uncertainty of G ?
    3) the unit of G is Pa right??


    3. The attempt at a solution i did the graph where i am supposed to make the uncertainty rectangles but the graph didnt work out too much for me especially that i repeated the experiment several times and i have the same answers ( with a small difference) so any suggestions
     
  2. jcsd
  3. Dec 3, 2011 #2
    It looks like yes to 3 but typical numbers for metal are 10's of giga Pa, 10E9 Pa see,

    http://www.engineeringtoolbox.com/modulus-rigidity-d_946.html

    from,

    https://www.google.com/webhp?hl=en#...w.,cf.osb&fp=2ddf388403c0c5d8&biw=734&bih=439

    For question 2 it looks like most error will come from a as it goes to the 4th power and it is most likely very small. What was a and to what fraction of an inch or mm did you measure, like wise for L.

    I think your answer to 1 is way off, are your lengths in meters or mm? Pascals are Newtons per m^2.
     
  4. Dec 4, 2011 #3
    so what i can see the number should be big
     
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